1. Field of the Invention
This invention relates to a device for supporting an optical system, and, more particularly, it is concerned with an improvement in the device for supporting the optical system such as an object lens or an optical head of a recording and reproducing apparatus, etc. in a manner to be movable in two-dimensional directions.
2. Description of the Prior Art
In an optical recording and reproducing apparatus, etc., it has heretofore been a practice to move its object lens at a high speed in the optical axis direction or a direction perpendicular to the optical axis so as to perform the automatic focus control for forming a light spot on a recording medium or the tracking control for letting the light spot trace the recording track. By such high speed movement of the object lens, etc., however, there arose such a problem that the optical axis of the object lens, etc. tends to tilt. With a view to removing such a problem, there has so far been made various proposals on the optical system supporting device, wherein the inclination of the object lens, etc. is reduced by utilization of a leaf spring, and the like. As examples for such device, there may be one as shown in FIG. 1 of the accompanying drawing, which is movable two-dimensionally; or another as shown in FIG. 2, which is movable in a single dimensional direction; or still another as shown in FIG. 3, which is movable three-dimensionally; and so forth.
In FIG. 1, the leaf springs 2a, 2b enable the object lens 1 to move in the direction of the optical axis, while the leaf springs 3a, 3b enable it to move in the direction perpendicular to the optical axis. A reference numeral 4 designates an intermediate supporting member, and a numeral 5 refers to a main body mounting plate. In FIG. 2, radially extending portions 7a, 7b of two leaf springs 6a, 6b, respectively, enable the object lens 1 to move in the direction of the optical axis. The annular portions of the leaf springs 6a, 6b are fixed to the main body. In FIG. 3, leaf springs 8a, 8b enable the object lens 1 to move in the lateral direction, leaf springs 9a, 9b in the vertical direction, and leaf springs 10a, 10b in the optical axis direction. A reference numeral 11 designates an intermediate supporting member, and numeral 13 refers to a main body mounting plate.
However, of these optical system supporting devices having such construction as mentioned above, those as shown in FIGS. 1 and 3 which support the object lens in a manner to be movable in two or three dimensional directions still involve problems such that they tend to cause the object lens to tilt readily, are inferior in their tracking characteristic at a high speed operation inasmuch as an object lens supporting part consisting of the leaf springs, etc. has a large moving quantity, are difficult to perform accurate and delicate control for very fine and small moving quantity, since the devices are not smooth in movement, and others, with the consequence that there has not yet been realized the optical system supporting device which is perfectly free from these disadvantages. A method, wherein the entire optical system including a photo-detector, etc., not to say of the object lens, is caused to move as an integral whole, has also been proposed. Even in this case, however, the same problems as mentioned above still remained.